1. Field of the Invention
The present invention relates broadly to telecommunications. More particularly, the present invention relates to means and methods for the collection of information regarding switched virtual circuit (SVC) calls in the ATM telecommunications network. The invention has particular application with respect to information which may be used to produce billing records used to invoice a customer, but is not limited thereto.
2. State of the Art
Perhaps the most awaited, and now fastest growing technology in the field of telecommunications in the 1990's is known as Asynchronous Transfer Mode (ATM) technology. ATM is providing a mechanism for removing performance limitations of local area networks (LANs) and wide area networks (WANs) and providing data transfers at a speed of on the order of gigabits/second. The variable length packets of LAN and WAN data are being replaced with ATM cells which are relatively short, fixed length packets. Because ATM cells can carry voice, video and data across a single backbone network, the ATM technology provides a unitary mechanism for high speed end-to-end telecommunications traffic.
In order for ATM technology to develop, it must be functional in its own right as well as compatible with existing technology. Thus, a technical group called the ATM Forum which is comprised of numerous corporate representatives has been proposing ATM specifications which are being provided to ANSI and the ITU-T for their consideration and adoption. Details of these specifications may be found in proceedings of the ATM Forum as well as the proceedings of ANSI and the ITU-T. Of particular interest among such documents for purposes herein is a document which is incorporated by reference in its entirety herein and which is entitled "Q.2726.3 Final Text, Broadband ISDN User Part, Network Call Correlation Identifier" under ITU-Telecommunication Standardization Sector Study Group 11, Data Miyazaki, Jan. 29-Feb. 16, 1996. The Q.2726.3 standards document incorporates the present invention which was described by this inventor on or about Jun. 5, 1995 to the ATM Forum, Technical Committee Working Groups (B-ICI, PNNI and Signalling) in Contribution ATMF/95-0632. Of additional interest for the present invention are ITU-T Standards document Q.2931 and ATM Forum specification UNI-3.1 which are hereby incorporated by reference herein in their entireties and relate to the UNI interface, as well as ATM Forum B-ICI Specification Version 2.0 and ITU-T B-ISUP signaling protocols in standards Q.2761, Q.2762, Q.2763, and Q.2764, all of which are hereby incorporated by reference herein in their entireties.
As set forth by the present inventor in the ATM Forum contribution 95-0632, in the specifications for SVC (switched virtual circuit) operation as had then existed, there was an implicit assumption that "usage based billing" could be utilized for SVC services, where "billing" means the collection of information relating to a call which provides details for the overall call rather than simply statistics from one point in the network. One fundamental requirement which had to be met in order to offer "usage based billing" was the ability to uniquely identify a call and the corresponding statistics associated with the call. At that time it was assumed that if a call was placed from a first user site (at a user-network interface site A or UNI A) to a second site (UNI B), both sites would have ATM end system addresses which would uniquely identify the relevant interfaces within the network. Thus, if an end system at the site connected to the network by UNI A made a call to an end system at the site connected by UNI B, then the CALL SETUP message would contain the address of UNI B as the called address and that of UNI A as the calling address. The switches supporting UNI A and UNI B would establish the call and internally maintain some form of call status record which would contain details relating to the call. At the end of the call, the information from the internal call status record would then be transferred to a billing record which could be processed by some form of external billing system. A key feature envisioned by such a system is that data would be collected at different points in the network (e.g., the switch providing UNI A and the switch providing UNI B) regardless of whether ingress or egress counts were to be used for the aggregate billing or statistics record. Of course, the switches could be in different provider networks linked by multiple PNNI and/or B-ICI interfaces.
With the assumed system, an external billing system would be presented with two records from different sources that relate to the same call. The information from those records could then be used in the final composite record. It was assumed that the different billing records from the different sources could be correlated by studying the information that they contained. For example, the called and calling addresses would be saved in each billing record and thus provide a mechanism to relate the records from the different system together. In addition, time stamp information (e.g., start time, duration, etc.) could be used to help relate different billing records together. However, the present inventor recognized that this information is not enough to guarantee that billing information from different sources would be correctly matched up.
In particular, a situation could occur where two calls originated from an end system connected via UNI A at the same time where both calls were destined for an end system connected by UNI B. The two calls would be processed in sequence by UNI A and two entries made in the switch call status table. After transiting the network, the two calls would be processed in sequence by UNI B and terminated to the relevant end system(s). However, it is perfectly possible that the two CALL SETUP messages might take different paths through the network, and thus, the first call processed by UNI A would not necessarily be the first processed by UNI B. This would suggest that timing information relating to call start time in the subsequent billing record could not be used to determine which record matched with which. Moreover, if both calls should happen to terminate at the same time (perhaps due to a link failure), the call duration information would likewise not help in matching billing records. Furthermore, as both calls originated from the same address and were destined for the same address, the address information could not be used to help in matching the subsequent billing records. Clearly, such a situation is not ideal.